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Reducing noise

From: Photoshop CS6 Image Cleanup Workshop

Video: Reducing noise

Now, this is certainly a photo that could use a little bit of clean up. But I'm actually not worried about all the mud on the car. That's half the reason I took the picture in the first place, but rather the noise. This image was captured at a very high ISO setting, 6400 ISO in this case. And whenever you increase the ISO setting on your camera, you're not actually increasing the sensitivity of the image sensor, but rather you're applying amplification to the signal that's being captured. Amplification results in noise and if we zoom in, especially in some of the darker areas of the image, you'll see quite a bit of noise.

Reducing noise

Now, this is certainly a photo that could use a little bit of clean up. But I'm actually not worried about all the mud on the car. That's half the reason I took the picture in the first place, but rather the noise. This image was captured at a very high ISO setting, 6400 ISO in this case. And whenever you increase the ISO setting on your camera, you're not actually increasing the sensitivity of the image sensor, but rather you're applying amplification to the signal that's being captured. Amplification results in noise and if we zoom in, especially in some of the darker areas of the image, you'll see quite a bit of noise.

Noise appears as random variations in pixel values and at a pixel level. So we're seeing very, very tiny changes within the image. You might not even notice noise from a distance, for example. And that noise can appear either as color variations or as luminance or brightness variations, or in many cases, both. Here, we can see that the color variations, the color noise, is the most significant issue. Let's take a look at how we can correct for noise. Now, your camera may include some options to help you minimize noise in the capture.

And you can also reduce noise in the raw conversion process if you're capturing in Raw. But we can also correct noise after the fact in Photoshop. Because noise reduction does alter pixel values in the image, I want to work in a non-disruptive way. And so I'm going to create a copy of my background image layer as a starting point. I'll go ahead and drag the thumbnail for my Background Image layer down to the Create New Layer button, the blank sheet of paper icon at the bottom of the Layers panel. That will create a background copy. I'm going to go ahead and double-click that name and I'll call this Noise Reduction. So, I know exactly why I've added this layer.

I'll then press Enter or Return on the keyboard to apply the name change. And then, to correct the noise, I'll choose Filter > Noise > Reduce Noise. That will bring up the Reduce Noise dialog. I'm going to zoom in a little bit more here. I usually work at around 400% or so, so that I can better evaluate the results in the image. And I also start by reducing the Strength Value and the Sharpen Details Value. And I'll even minimize the Reduce Color Noise Value, so that I can see the image with absolutely no noise reduction at all.

I'll then start with my color noise reduction. I'll drag the Reduce Color Noise slider over to the right. And you can see that as I do so, that color noise starts to disappear. You might be tempted to move that slider all the way over to the right, but the problem is, if you apply too much noise reduction, you'll be averaging out color values within the image. And you can actually reduce saturation in certain areas. I'll go ahead and pan across the image for example. And you can see that this portion of the image is looking rather gray, whereas, there is a fair amount of color in the original image. And that's not just because of the noise.

So, we're reducing the color in the image pretty significantly. My general rule of thumb, is to apply only as much as color noise reduction as you actually need in order to produce a good result in the image. For this photo, I do need a rather strong effect, so it looks like at right about 55% is producing a good result. If I click and hold my mouse in the Preview, I can see the before version of the image. And if I release the mouse, I'll see the after version. If there is considerable detail in the image, I'll go ahead and drag across the image to the headlight, for example, which will show us a reasonable amount of detail.

I can bring back some of that detail with the Sharpen Details option. I'll move that slider over to the right. And you can see that I'm able to exaggerate some of that detail a little bit. That, of course, creates an appearance of luminance noise, so I don't want to use too strong a value, but a little but, so that we bring back some of that detail, compensating for the loss of sharpness that can occur when we reduce noise. I'll then pan across the image a little bit. And in fact, I'll move the Reduce Noise slider over to the right, so that I can see more of the image. And then, I'll click on a dark area in the image so that I can set that as my preview area.

And then, we'll take a look at the strength slider, which reduces luminance noise. I'll go ahead and drag that all the way over to the right, and then we'll pan around the image a little bit. And you can see, between the before and after, if I move the slider left and right for example A little bit of a change. In this image, there's not too much in the way of luminance noise, but it's also being masked a little bit because I have the Preserve Details slider up at 60%. I'll set that down to 0. And now, you can see that the noise reduction is actually softening the image rather significantly. So, once again, by reducing that Preserve Detail slider, I can get a better sense of just how much noise reduction I want to apply.

In this case, I think right about three is going to be the limit. But then I will increase the Preserve Detail slider to bring back some of the original texture in the photo. If the image is a JPEG capture, you can also turn on the Remove JPEG Artifact checkbox in order to even out some of the Artifacts caused by JPEG images. Quite frankly, in many cases, I find this check box actually reduces the quality of the image. And so I generally turn it on or off to decide which option I refer. In this case, I think the image actually looks better with that option turned off, even though, I'm working with a JPEG image.

In addition to the basic settings, we can switch to the Advanced mode and then apply Per Chanel noise reduction. In most cases, you'll find that the blue channel is the worst offender when it comes to noise. I'll go ahead and click on that blue channel and then release. And you can see that there's quite a bit of noise on the blue channel. So, we could increase the strength for the blue channel all by it's self and adjust the Preserve Detail setting as needed in order to optimize that blue channel. In most cases, I think it's perfectly fine to simply work on the overall settings. But with certain images, especially images that were a little under exposed, you might find that the Per Channel option.

Provides a greater agree of control to help improve the result that you're able to achieve. But I think, in this case, we've got a good result. I'll go ahead and click the OK button. And I can zoom out on the image and turn off the Noise Reduction layer and turn it back on. And even there, you might be able to see a bit of a difference. But zooming in, we can most certainly see a difference between the before and after. So, a significant improvement in this photo that exhibited considerable noise when we got started.

Show transcript

This video is part of

Image for Photoshop CS6 Image Cleanup Workshop
Photoshop CS6 Image Cleanup Workshop

30 video lessons · 1499 viewers

Tim Grey
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